Dewaxing hydrocarbon oil



Patented Sept. 15, 1936 PATENT OFFICE.

DEWAXING HYDROCARBON OIL Edwin C. Knowles, Beacon, N. Y., assignor toThe Texas Company, New York, N. Y., a cornotation of Delaware NoDrawing. Application May 7, 1935, Serial No. 20,193

5 Claims.

This invention relates to dewaxing hydrocarbon oil and more particularlyto the removal of wax from mineral lubricating oil stock for theproduction of low pour test lubricating oil.

The invention broadly contemplates dewaxing wax-bearing mineral oil witha solvent composed of mixed aliphatic ketones, and particularly amixture composed of a high molecular weight member of the series ofaliphatic ketones and a relatively low molecular weight member of thesame series.

More specifically, the invention comprises -dewaxing oil with a mixtureof an aliphatic ketone having around seven to ten carbon atoms and arelatively lower member of the series having up to six carbon atoms.

I have discovered that the higher members of the series of aliphaticketones having from seven up to about ten carbon atoms have :acomparatively high solvent power for mineral oil "at temperatures ofthe'order of 0 F. and below. I have found that the solubility of mineraloil is greater in these higher members of the aliphatic ketones than inthe relatively lower members of the series having fewer carbon atoms.Due to the high solubility of oil in these compounds, they are,therefore, suitable as good oil solvents and provide, when mixed with awax anti-solvent liquid, a selective solvent liquid mixture which isparticularly well adapted for the dewa'xing of hydrocarbon oil.

The aliphatic ketones having this characteristic 'of high oil solubilitycomprise dipropyl ketone, propyl isobutyl ketone, methyl normal hexy-lketone, ethyl normal amyl ketone and ethyl iso-amyl ketone. Dipropylketone, for example, has the following chemical formula: C3H1COC3H'1,while methyl normal hexyl ketone, for example, has the formula:CH3COC6H13.

Higher molecular weight members of the series such as ethyl hexylketone, propyl hexyl ketone (containing nine and ten carbon atoms), eventhough they are solids at temperatures below about 25 F., maynevertheless be used in combination with a relatively lower member ofthe series to provide a satisfactory dewaxing solvent. For example, thesolid point of a mixture of such high molecular weight ketone withacetone or methyl ethyl ketone is depressed below normal dewaxingtemperatures.

The lower members of the series of aliphatic ketones which are suitableas wax anti-solvent liquids comprise acetone, methyl ethyl ketone andmethyl isobutyl ketone.

Methyl isobutyl ketone which contains six carbon atoms combines theproperties of wax antisolvent action and good oil solvent action to aconsiderable extent. However, I have found that when this compound ismixed with a higher member of the series of aliphatic ketones, such asdipropyl ketone, and which has a relatively higher solubility for oil,an improved dewaxi-ng solvent liquid mixture is obtained. Such a mixturemay be used for dewaxing at relatively lower temperatures than methylisobutyl ketone alone, 1 0 and when used at temperatures relativelybelow 0 F., this mixture continues to exert a solvent action uponsubstantially all of the liquid oil constituents.

My invention, therefore, comprises mixing wax- 15 bearing oil with asolvent composed of an aliphatic ketone having around seven to tencarbon atoms, and an aliphatic ketone having up to six carbon atoms, insuch proportion that at temperatures of 0 F. and below, the solvent mix-.20 ture has substantially complete solvent action on the liquidconstituents of oil, and substantially no solvent action upon the solidwaxy constituents of the oil. This mixture of oil and solvent liquid ischilled to temperatures of 0 F. and below, depending upon the desiredpour test of the dewaxed oil to precipitate the wax constituents. Thewax constituents thus precipitated are then separated from the coldmixture by mechanical means, such as filtration, centrifuging, $0 orsettling.

In order to more clearly describe the invention, reference will now bemade to the following examples in which a wax-bearing distillate,solvent refined to remove naphthenic 'constitu- 335 ents, and derivedfrom a Mid-Continent crude and also having the following tests, wasdewaxed with a mixture comprising dipropyl ketone and a wax anti-solventliquid, consisting of a relatively lower molecular weight ketone: 40

Gravity A. P. I 26.9 Saybolt universal viscosity seconds at 210 F 112 7Pour test F 120 45 In the first example, one part of the above oil wasmixed with four parts by volume of a solvent liquid mixture consistingof 20% dipropyl ketone and methyl isobutyl ketone. This mixture was thenchilled to a temperature of --10 F. to precipitate wax constituents.Thereafter, the mixture was subjected to filtration to separate andremove the precipitated wax constituents.

The solvent liquid was then removed from the filtrate by distillation,leaving a dewaxed oil 55 which comprised about 61% of the wax bearingoil. This dewaxed oil had a pour test of 10 F., or a pour testcorresponding to the temperature at which it was dewaxed. I

In the second example, one volume of the same wax-bearing oil was mixedwith four volumes of a solvent liquid mixture consisting of equal partsof dipropyl ketone and methyl ethyl ketone. This mixture was chilled toa temperature of 0 F. to precipitate the wax constituents and at thistemperature it was filtered. After removal of the solvent from theresulting filtrate, the dewaxed oil was found to have a pour test of 0F.

The precipitate of slack was removed in the dewaxing of the aboveexamples contained wax having a melting point of around to 147 F. andcomprising about 41 to 44% of the slack wax precipitate removed from thesolvent mixture.

Rapid rates of filtration were realized in each case, and theprecipitated wax was found to be readily filterable.

While in the foregoing examples, dewaxing with solvent liquid mixturescomposed of dipropyl ketone with methyl ethyl ketone and methyl isobutylketone have been specifically described, the invention is not restrictedto these particular mixtures. As already indicated, dipropyl ketone maybe used in conjunction with lower members of the series of aliphaticketones as, for example, acetone. On the other hand, instead of dipropylketone, higher members of the aliphatic series may be employed, such asmethyl 'hexyl ketone and ethyl amyl ketone.

Nor is the invention restricted to the dewaxing of solvent refineddistillates, such as that referred to above, but may be applied to thedewaxing or separation of wax from other fractions of crude petroleum,either residual or distillate. Furthermore, the proportions of theindividual solvents, comprising the dewaxing mixture as well as theproportion of the solvent mixture to the oil undergoing dewaxing, willvary, depending upon the oil and wax content of the particular materialundergoing treatment.

7 Obviously, many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the ap pended claims. Y

I claim: 7

1. In the dewaxing of wax-bearing mineral oil, the method whichcomprises mixing the oil with a solvent comprising an aliphatic ketonehaving around seven to ten carbon atoms in admixture with an aliphaticketone having up to six carbon atoms in proportions such that attemperatures of 0 F. and below, the mixture has substantially completesolvent action on the liquid constituents of the oil and substantiallyno sol,- vent action upon the solid waxy constituents of the oil,chillingthe mixture to a temperature of 0 F. and below to precipitatethe wax constituents, and separating the thus precipitated waxconstituents from the cold mixture.

2. In the dewaxing of wax-bearing mineral oil, the method whichcomprises mixing the oil with a solvent composed of an aliphatic ketonehaving around seven to ten-carbon atoms in admixture with a waxanti-solvent liquid of the character of methyl ethyl ketone inproportions such that at temperaturesof 0 F. and below, the mixture hassubstantially complete solvent action on the liquid constituents of theoil and substantially no solvent action upon the solid waxy constituentsof the oil, chilling the mixture to a temperature of 0 F. and below toprecipitate the wax constituents, and separating the thus precipitatedWax constituents from the cold mixture;

3. In the dewaxing of wax-bearing mineral oil, the method whichcomprises mixing the .oil with a solvent liquid comprising dipropylketone, chilling the mixture to precipitate the wax constituents, andseparating the thus precipitated wax constituents from the cold mixture.

4. In the dewaxing of wax-bearing. mineral oil,

the method Which comprises mixing the oil with a solvent composed ofdipropyl ketoneandmethyl isobutyl ketone in proportions such that attemperatures of 0 Rand below the mixture has substantially completesolvent action on the liquid constituents of the oil .and substantiallyno solvent action upon the solid waxy constituents of the oil, chillingthe mixture to a temperature of 0 F. and below to precipitate the waxconstitue ents, and separating the thus precipitated wax constituentsfrom the cold mixture.

5. In the dewaxing of wax-bearing mineral oil, the method whichcomprises mixing the oilwith a solv-entcomposed of dipropyl ketone andmethyl ethyl ketone in proportions such that at. temperatures of 0 F.and below the mixture has substantially complete solvent action ontheliquid constituents of the oil and substantially no solvent actionupon the solid waxy constituents of the oil, chilling the .mixture to .atemperature of 0 F. and below to precipitate the wax constituents, andseparating the thus'precipitated wax constituents fromthe cold mixture.

EDWIN C. KNOWLES.

